Later the group of Bartoov introduced the IMSI (intracytoplasmic morphologically selected sperm injection) (Bartoov B., et al., 2003), allowing the single microinjection of selected motile spermatozoa with strictly defined morphologically normal nuclei into the cytoplasm of retrieved oocytes. This prospective controlled study, performed in couples with male infertility and at least two previous failed ICSI attempts, showed that IMSI resulted in a significantly higher pregnancy and implantation rate as compared with conventional ICSI. From their results they assume that in the IMSI, the survival of the embryo in the uterus is associated with the fine morphological state of the sperm nucleus.